1. Field of the Invention
The present invention is broadly concerned with improved apparatus and methods for the injection of solid treatment pellets into producing oil and gas wells. More particularly, the invention is concerned with such apparatus and methods which make use of high pressure liquid flow serving to entrain solid pellets from a source thereof, for ultimate delivery to the producing well. The apparatus may advantageously be truck-mounted so that pellets of the desired type may be easily injected at the well head.
2. Description of the Prior Art
Oil and gas wells sometimes require the periodic addition of treatment agents, such as scale and corrosion inhibitors, in order to facilitate smooth, trouble-free operations. Such agents are often in liquid form, and are commonly added into the annular space between the well sidewall and the internal well casing. Well operators use a number of expedients for such additions, such as introduction through a side arm flush associated with the well fluid removal system. Because conventional treating agents tend to float on the well fluid, it is a common practice to add excess well fluid after addition of the treatment agent in order to drive the agent downwardly to a subterranean level adjacent the lower end of the well casing. As can be appreciated, this practice largely or completely shuts down well production, and it is not uncommon to thereby lose an entire day's production during the treatment process.
Solid treatment composites in the form of pellets or the like have also been utilized to provide a method for downhole treatment. For example, mold inhibitors such as the commercial product Iconol NP-100 Pastille FD (a nonylphenol ethoxylate available from BASF Corp.) have been mixed with active ingredients (such as corrosion inhibitors or bactericides) and formed into pellets. Also, U.S. Pat. No. 6,135,207 describes solid, self-sustaining well-injection pellets which can be formulated as corrosion and/or scale inhibitors, bactericides, or foaming agents. Pellets of this type have been commercialized by Jacam Chemical Company 2013, LLC, of Sterling, Kans.
Injection of solid treatment pellets can present a problem during the operation of a producing well. This is because these wells are often of relatively high pressure, ranging anywhere from 1,000-10,000 psi or above. Attempts have been made to simply dump treatment pellets into an above ground tank or sump for well fluids, but, in many instances, this expedient is unsuccessful because the pellets must be injected in a way to overcome the existing well pressures.
Pump arrangements have been devised for propelling pellets into wells, see, e.g., U.S. Pat. No. 2,790,500. The '500 patent discloses a pump arrangement wherein spherical treatment balls are mechanically propelled into a flow line using a spring-loaded piston assembly. This type of device is not suitable for elongated pellets, which are commonly produced today, and moreover does not generate adequate forces for very high pressure wells.
There is accordingly a need in the art for improved apparatus and methods for the injection of solid well treatment pellets of any type, and which overcomes the drawbacks of the prior art.